The present invention relates generally to the packaging of integrated circuits in micro-array style packages.
There are a number of conventional processes for packaging integrated circuits. Many packaging techniques use a leadframe that has been stamped or etched from a metal (typically copper) sheet to provide electrical interconnects to external devices. One relatively recently developed packaging style, which is sometimes referred to as a leadframe based micro-array package is generally illustrated in FIG. 1. In a micro-array package, the leadframe typically includes an array of contact posts 22 that are exposed on the bottom surface of the package and lead traces 24 that may or may not be exposed at the bottom surface of the package. A die mounted on the lead frame is wire bonded (or otherwise electrically connected) to the lead traces, which serve as electrical connectors between the bonding wires and the contact posts 22. Often the micro-array package will also have a die support structure 26 that supports the die.
Micro-array packages have a number of potential advantages. For example, they are relatively low cost, they may be configured to be pin compatible with conventional BGA packages and they allow a relatively large number of contacts for a given package size. Also, since the lead traces permit “routing” of signals to contact pads located under the die, a package with a relatively smaller footprint may be used for a given die size and pin count as compared to many other leadframe based packages.
Some micro-array packaging approaches have dispensed with the lead traces and formed contact posts or pads that can be directly wire bonded to. By way of example, U.S. Pat. Nos., 6,683,368; 6,689,640; and 6,812,552 disclose such approaches. In these approaches, the lead frame is typically partially etched in order to define the contact pads that are supported by a thin connecting sheet that remains due to the partial etching. Dice are then mounted on and electrically connected to the lead frame and an encapsulant is molded (or otherwise dispensed) over the dice to form appropriate package structures. After the molding, the connecting sheet is etched away thereby leaving the contact pads exposed on the bottom surface of the package.
Given their many advantages, micro-array packages in general have recently generated a great deal of interest within the semiconductor industry. Although existing techniques for fabricating micro-array leadframes and for packaging integrated circuits using micro-array leadframe technology work well, there are continuing efforts to develop even more efficient designs and methods for packaging integrated circuits using micro-array leadframe technology.